Emission control systems are well known in the art for connecting an exhaust suction hose to the exhaust or tail pipe of a vehicle. One such system is the SYMPLAIR.TM. S20 vehicle emission capture system manufactured by Tykron Inc. of Grimsby, Ontario. This prior art system includes ductwork which extends from one side of a swivel ball to a fan which in turn discharges fumes from within a structure. The other side of the swivel ball is connected to a flexible exhaust hose which has a free end spaced away from the swivel ball. An intermediate portion of the flexible hose is supported by a spring take-up reel carried by a trolley on a suitable track. The free end of the exhaust hose of the SYMPLAIR.TM. S20 vehicle emission capture system carries a pliers-like clamping device which may be used to secure the free end of the flexible hose to the exhaust pipe of a vehicle. The pliers-like coupling device has been developed so that as the vehicle exits from the structure the coupling device will disconnect from the exhaust pipe of the vehicle. This type of system allows mobility of a vehicle over a limited range within a structure, and has the advantage of discharging exhaust fumes from within the structure when the vehicle is operated within the structure. The SYMPLAIR.TM. S20 vehicle emission capture system finds particular application in fire stations where it is desirable that vehicles should be exhausted up to the point where they leave the building, thereby preventing contamination of the firemen's on site living quarters, which are frequently above the vehicle bays. While the SYMPLAIR.TM. S20 vehicle emission capture system has performed satisfactorily, the mechanical pliers-like coupling device has not always performed in a satisfactory manner when the vehicle is exiting the structure. The principal disadvantage of the pliers-like coupling device has been that the metal parts have been shown to occasionally damage the finish of expensive equipment, such as for example a fire vehicle. On rare occasions, when the coupling device has not been properly attached, damage to the exhaust system has occurred.
To overcome the deficiencies of the foregoing type of mechanical attachment device, an alternative connection system has been developed which is shown in U.S. Pat. No. 5,162,017. In this device an intermediate portion of the flexible exhaust suction hose carries an electromagnet which is adapted to be coupled to a specific site on the vehicle, there being a leaf spring extending from the area of the electromagnet to free end of the flexible hose, the leaf spring being designed to maintain the free end of the suction hose about the end of the exhaust pipe of the vehicle. Although this form of device eliminates some of the disadvantages of the prior art, it adds complications in that the electromagnet does not always properly disconnect as the vehicle is exiting the structure. In addition, such a device tends to be more expensive than other prior art.
One of the disadvantages of the SYMPLAIR.TM. S20 vehicle emission capture system, as well as the system shown in U.S. Pat. No. 5,162,017, is that as the vehicle moves, the hose tends to twist about its axis making the alignment of the disconnect difficult to achieve. In this regard it should be noted that the angle at which the hose is pulled from the vehicle effects the disconnect.